Microwave transmitters and other communication equipment commonly employ RF power couplers, sometimes referred to as dividers, for electromagnetically coupling a portion of the energy flowing in one circuit to a second circuit. One previous type of power coupler commonly employed is depicted in FIGS. 1, 2 and 3 to which reference will now be made. The prior coupler includes an electrically conductive metal base 10 having a pair of generally U-shaped slots 12, 14 formed therein which intersect at a central juncture generally indicated at 23. A pair of conductors 16, 18 which are rectangular in cross-section (See FIG. 2) are supported within the corresponding slots 12, 14 by means of rings 20 of insulative material which are sleeved over the conductors 16, 18. The conductors 16, 18 include essentially straight bases 16a, 18a at the juncture 23 which are held in spaced apart relationship by means of a rectangular spacer 22 which is best seen in FIG. 3. The spacer 22 is formed of a high dielectric constant material and is provided with a central, rectangular cutout 25 through which electromagnetic energy is transferred. Raised lands 24 on the body of the spacer 22 control the precise spacing between the bases 16a, 18a. The bases 16a, 18a are biased toward each other and into engagement with the spacer 22 by means of bearing members 26 which are captured between the legs of the corresponding conductor 16, 18 and a tubular spring 28.
The prior art coupler described above suffers from a number of deficiencies which substantially limit the efficiency of the coupler, both in terms of its power coupling capacity and thermal efficiency, as well as the coupler's mechanical stability. The power handling capacity of the coupler is primarily limited by a phenomenon known as multipacting. Multipacting occurs under relatively high radio frequency power conditions where a very high alternating field strength is set up in a confined volume representing a tuned resonance circuit. The result of multipacting is arcing between the conductors which degrades and damages the faces of the conductors.
The supporting rings employed in the previous coupler are less than totally effective in preventing lateral movement of the conductors 16, 18 relative to each other. Such lateral movement affects the alignment between the conductors thereby degrading power coupling efficiency. Additionally, the power handling capacity of the previous coupler is severely limited since the spacer 23 employs an air dielectric between the conductors through which the electromagnetic energy is transferred.